Louis E. S. Hoffenberg, Alexander Khrabry, Yuri Barsukov, Igor D. Kaganovich, David B. Graves
Metallic nanoclusters are of interest in many fields because of their size-dependent catalytic activity. This activity can, in part, be influenced by their melting properties. In this work, the melting phase transitions of $Fe_{n}$ nanoclusters with $n leq 100$ atoms were investigated using classical many-body molecular dynamics simulations. Adding a single atom to many cluster sizes induced strong variations in melting point ($T_{melt}$), latent heat of melting ($Delta H_{melt}$), and onset temperature of isomerization ($T_{iso}$). Clusters with size-dependent melting behavior were classified into 3 distinct cluster types: closed-shell, near-closed-shell, and far-from-closed-shell clusters. First-order-like phase transitions were observed only for cluster sizes with particularly symmetric closed shells and near-closed shells with up to a few missing or extra atoms. Near-closed-shell clusters had very low $T_{iso}$ relative to their $T_{melt}$. Far-from-closed-shell clusters exhibited second-order-like phase transitions. Variations in the melting and isomerization behavior of neighboring cluster sizes may have implications for catalytic systems such as the growth of single-wall carbon nanotubes.
{"title":"Types of Size-Dependent Melting in Fe Nanoclusters: a Molecular Dynamics Study","authors":"Louis E. S. Hoffenberg, Alexander Khrabry, Yuri Barsukov, Igor D. Kaganovich, David B. Graves","doi":"arxiv-2409.02293","DOIUrl":"https://doi.org/arxiv-2409.02293","url":null,"abstract":"Metallic nanoclusters are of interest in many fields because of their\u0000size-dependent catalytic activity. This activity can, in part, be influenced by\u0000their melting properties. In this work, the melting phase transitions of\u0000$Fe_{n}$ nanoclusters with $n leq 100$ atoms were investigated using classical\u0000many-body molecular dynamics simulations. Adding a single atom to many cluster\u0000sizes induced strong variations in melting point ($T_{melt}$), latent heat of\u0000melting ($Delta H_{melt}$), and onset temperature of isomerization\u0000($T_{iso}$). Clusters with size-dependent melting behavior were classified into\u00003 distinct cluster types: closed-shell, near-closed-shell, and\u0000far-from-closed-shell clusters. First-order-like phase transitions were\u0000observed only for cluster sizes with particularly symmetric closed shells and\u0000near-closed shells with up to a few missing or extra atoms. Near-closed-shell\u0000clusters had very low $T_{iso}$ relative to their $T_{melt}$.\u0000Far-from-closed-shell clusters exhibited second-order-like phase transitions.\u0000Variations in the melting and isomerization behavior of neighboring cluster\u0000sizes may have implications for catalytic systems such as the growth of\u0000single-wall carbon nanotubes.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ilia SmirnovUniversity of Warsaw, Warsaw, Poland, Zbigniew KaszkurInstitute of Physical Chemistry, Warsaw, Poland, Riccardo FerrandoUniversity of Genoa, Genoa, Italy
Stacking defects in noble metal nanoparticles significantly impact their optical, catalytic, and electrical properties. While some mechanisms behind their formation have been studied, the ability to deliberately manipulate nanoparticle bulk morphology remains largely unexplored. In this work, we introduce a pioneering mechanism - vacancy-driven twinning - that enables the transformation of face-centered cubic (fcc) gold into locally hexagonal close-packed (hcp) structures. This innovative approach, demonstrated through computational simulations, facilitates the creation of realistic , randomly multi-twinned nanoparticle models. By employing a recently developed multidomain X-ray diffraction method (MDXRD), we quantitatively assess the degree of twinning. It is a crucial step in transferring theoretical studies into practical applications. Our work aims to develop tools for modifying and controlling the bulk structure of fcc nanoparticles
贵金属纳米粒子中的堆叠缺陷会严重影响其光学、催化和电学特性。虽然人们已经研究了缺陷形成背后的一些机制，但有意操纵纳米粒子体态的能力在很大程度上仍未得到探索。在这项工作中，我们介绍了一种开创性的机制--空位驱动孪晶--它能使面心立方（fcc）金转变为局部六方紧密堆积（hcp）结构。这种创新方法通过计算模拟得到了证实，有助于创建逼真的随机多孪晶纳米粒子模型。通过采用最新开发的多域 X 射线衍射方法（MDXRD），我们对孪晶程度进行了定量评估。这是将理论研究转化为实际应用的关键一步。我们的工作旨在开发修改和控制 fcc 纳米粒子块体结构的工具
{"title":"How to manipulate nanoparticle morphology with vacancies","authors":"Ilia SmirnovUniversity of Warsaw, Warsaw, Poland, Zbigniew KaszkurInstitute of Physical Chemistry, Warsaw, Poland, Riccardo FerrandoUniversity of Genoa, Genoa, Italy","doi":"arxiv-2409.01254","DOIUrl":"https://doi.org/arxiv-2409.01254","url":null,"abstract":"Stacking defects in noble metal nanoparticles significantly impact their\u0000optical, catalytic, and electrical properties. While some mechanisms behind\u0000their formation have been studied, the ability to deliberately manipulate\u0000nanoparticle bulk morphology remains largely unexplored. In this work, we\u0000introduce a pioneering mechanism - vacancy-driven twinning - that enables the\u0000transformation of face-centered cubic (fcc) gold into locally hexagonal\u0000close-packed (hcp) structures. This innovative approach, demonstrated through\u0000computational simulations, facilitates the creation of realistic , randomly\u0000multi-twinned nanoparticle models. By employing a recently developed\u0000multidomain X-ray diffraction method (MDXRD), we quantitatively assess the\u0000degree of twinning. It is a crucial step in transferring theoretical studies\u0000into practical applications. Our work aims to develop tools for modifying and\u0000controlling the bulk structure of fcc nanoparticles","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sabrina Juergensen, Jean-Baptiste Marceau, Chantal Mueller, Eduardo B. Barros, Patryk Kusch, Antonio Setaro, Etienne Gaufrès, Stephanie Reich
Nanotubes align molecules into one dimensional chains creating collective states through the coupling of the molecular transition dipole moments. These collective excitations have strong fluorescence, narrow bandwidth, and shifted emission/absorption energies. We study the optical properties of {alpha}-sexithiophene chains in boron nitride nanotubes by combining fluorescence with far- and near-field absorption spectroscopy. The inner nanotube diameter determines the number of encapsulated molecular chains. A single chain of {alpha}-sexithiophene molecules has an optical absorption and emission spectrum that is red-shifted by almost 300 meV compared to the monomer emission, which is much larger than expected from dipole-dipole coupling. The collective state splits into excitation and emission channels with a Stokes shift of 200 meV for chains with two or more files. Our study emphasises the formation of a delocalized collective state through Coulomb coupling of the transition moments that shows a remarkable tuneability in transition energy.
{"title":"Collective states of α-sexithiophene chains inside boron nitride nanotubes","authors":"Sabrina Juergensen, Jean-Baptiste Marceau, Chantal Mueller, Eduardo B. Barros, Patryk Kusch, Antonio Setaro, Etienne Gaufrès, Stephanie Reich","doi":"arxiv-2408.15885","DOIUrl":"https://doi.org/arxiv-2408.15885","url":null,"abstract":"Nanotubes align molecules into one dimensional chains creating collective\u0000states through the coupling of the molecular transition dipole moments. These\u0000collective excitations have strong fluorescence, narrow bandwidth, and shifted\u0000emission/absorption energies. We study the optical properties of\u0000{alpha}-sexithiophene chains in boron nitride nanotubes by combining\u0000fluorescence with far- and near-field absorption spectroscopy. The inner\u0000nanotube diameter determines the number of encapsulated molecular chains. A\u0000single chain of {alpha}-sexithiophene molecules has an optical absorption and\u0000emission spectrum that is red-shifted by almost 300 meV compared to the monomer\u0000emission, which is much larger than expected from dipole-dipole coupling. The\u0000collective state splits into excitation and emission channels with a Stokes\u0000shift of 200 meV for chains with two or more files. Our study emphasises the\u0000formation of a delocalized collective state through Coulomb coupling of the\u0000transition moments that shows a remarkable tuneability in transition energy.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alexandre Boucher, Cameron Beevers, Bertrand Gauthier, Alberto Roldan
Computational modeling is an integral part of catalysis research. With it, new methodologies are being developed and implemented to improve the accuracy of simulations while reducing the computational cost. In particular, specific machine-learning techniques have been applied to build interatomic potential from ab initio results. Here, We report an energy-free machine-learning calculator that combines three individually trained neural networks to predict the energy and atomic forces of particulate matter. Three structures were investigated: a monometallic nanoparticle, a bimetallic nanoalloy, and a supported metal crystallites. Atomic energies were predicted via a graph neural network, leading to a mean absolute error (MAE) within 0.004 eV from Density Functional Theory (DFT) calculations. The task of predicting atomic forces was split over two feedforward networks, one predicting the force's norm and another its direction. The force prediction resulted in a MAE within 0.080 eV/A against DFT results. The interpretability of the graph neural network predictions was demonstrated by underlying the physics of the monometallic particle in the form of cohesion energy.
计算建模是催化研究不可或缺的一部分。随着它的发展，人们正在开发和实施新的方法，以提高模拟的准确性，同时降低计算成本。特别是，特定的机器学习技术已被用于根据原子序数结果建立原子间势。在此，我们报告了一种无能量机器学习计算器，它结合了三个单独训练的神经网络来预测微粒物质的能量和原子力。我们研究了三种结构：单金属纳米粒子、双金属纳米合金和支撑金属晶体。通过图神经网络预测了原子能量，与密度函数理论（DFT）计算结果相比，平均绝对误差（MAE）在 0.004 eV 以内。预测原子力的任务由两个前馈网络分担，一个预测力的标准，另一个预测力的方向。力预测结果与 DFT 结果的最大误差在 0.080 eV/Aagainst 范围内。图神经网络预测的可解释性通过以内聚能形式为基础的单金属粒子物理学得到了证明。
{"title":"Accelerated structure-stability energy-free calculator","authors":"Alexandre Boucher, Cameron Beevers, Bertrand Gauthier, Alberto Roldan","doi":"arxiv-2408.14577","DOIUrl":"https://doi.org/arxiv-2408.14577","url":null,"abstract":"Computational modeling is an integral part of catalysis research. With it,\u0000new methodologies are being developed and implemented to improve the accuracy\u0000of simulations while reducing the computational cost. In particular, specific\u0000machine-learning techniques have been applied to build interatomic potential\u0000from ab initio results. Here, We report an energy-free machine-learning\u0000calculator that combines three individually trained neural networks to predict\u0000the energy and atomic forces of particulate matter. Three structures were\u0000investigated: a monometallic nanoparticle, a bimetallic nanoalloy, and a\u0000supported metal crystallites. Atomic energies were predicted via a graph neural\u0000network, leading to a mean absolute error (MAE) within 0.004 eV from Density\u0000Functional Theory (DFT) calculations. The task of predicting atomic forces was\u0000split over two feedforward networks, one predicting the force's norm and\u0000another its direction. The force prediction resulted in a MAE within 0.080 eV/A\u0000against DFT results. The interpretability of the graph neural network\u0000predictions was demonstrated by underlying the physics of the monometallic\u0000particle in the form of cohesion energy.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Francisco Eduardo Rojas-González, Jorge Padilla-Alvarez, César Castillo-Quevedo, Rajagopal Dashinamoorthy Eithiraj, Jose Luis Cabellos
Understanding the properties of Au$_{10}$ clusters entails identifying the lowest energy structure at cold and warm temperatures. While functional materials operate at finite temperatures, energy computations using density functional theory are typically performed at zero temperature, resulting in unexplored properties. Our study undertook an exploration of the potential and free energy surface of the neutral Au$_{10}$ nanocluster at finite temperatures by employing a genetic algorithm combined with density functional theory and nanothermodynamics. We computed the thermal population and infrared Boltzmann spectrum at a finite temperature, aligning the results with validated experimental data. The Zero-Order Regular Approximation (ZORA) gave consideration to relativistic effects, and dispersion was incorporated using Grimme's dispersion D3BJ with Becke-Johnson damping. Moreover, nanothermodynamics was utilized to account for temperature contributions. The computed thermal population strongly supports the dominance of the 2D elongated hexagon configuration within a temperature range of 50 to 800 K. Importantly, at a temperature of 100 K, the calculated IR Boltzmann spectrum aligns with the experimental IR spectrum. Lastly, the chemical bonding analysis on the lowest energy structure indicates a closed-shell Au-Au interaction with a weak or partially covalent character.
要了解 Au$_{10}$ 团簇的性质，就必须确定其在低温和高温下的最低能量结构。虽然功能材料是在有限温度下工作的，但使用密度功能理论进行的能量计算通常是在零温度下进行的，这就导致了未探索的性质。我们的研究采用遗传算法，结合密度泛函理论和纳米热力学，探索了中性 Au$_{10}$ 纳米团簇在有限温度下的势能和自由能面。我们计算了有限温度下的热种群和红外玻尔兹曼频谱，并将结果与经过验证的实验数据进行了比对。零阶正则近似法（ZORA）考虑了相对论效应，并使用带有贝克-约翰逊阻尼的格里姆色散 D3BJ 纳入了色散。此外，还利用纳米热力学来考虑温度贡献。重要的是，在温度为 100 K 时，计算得出的红外玻尔兹曼光谱与实验得出的红外光谱一致。最后，对最低能量结构的化学键分析表明，闭壳金-金相互作用具有弱共价或部分共价性质。
{"title":"Structures and infrared spectroscopy of Au$_{10}$ cluster at different temperatures","authors":"Francisco Eduardo Rojas-González, Jorge Padilla-Alvarez, César Castillo-Quevedo, Rajagopal Dashinamoorthy Eithiraj, Jose Luis Cabellos","doi":"arxiv-2408.13451","DOIUrl":"https://doi.org/arxiv-2408.13451","url":null,"abstract":"Understanding the properties of Au$_{10}$ clusters entails identifying the\u0000lowest energy structure at cold and warm temperatures. While functional\u0000materials operate at finite temperatures, energy computations using density\u0000functional theory are typically performed at zero temperature, resulting in\u0000unexplored properties. Our study undertook an exploration of the potential and\u0000free energy surface of the neutral Au$_{10}$ nanocluster at finite temperatures\u0000by employing a genetic algorithm combined with density functional theory and\u0000nanothermodynamics. We computed the thermal population and infrared Boltzmann\u0000spectrum at a finite temperature, aligning the results with validated\u0000experimental data. The Zero-Order Regular Approximation (ZORA) gave\u0000consideration to relativistic effects, and dispersion was incorporated using\u0000Grimme's dispersion D3BJ with Becke-Johnson damping. Moreover,\u0000nanothermodynamics was utilized to account for temperature contributions. The\u0000computed thermal population strongly supports the dominance of the 2D elongated\u0000hexagon configuration within a temperature range of 50 to 800 K. Importantly,\u0000at a temperature of 100 K, the calculated IR Boltzmann spectrum aligns with the\u0000experimental IR spectrum. Lastly, the chemical bonding analysis on the lowest\u0000energy structure indicates a closed-shell Au-Au interaction with a weak or\u0000partially covalent character.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Remote sensing observations by Hayabusa2 and laboratory measurements have revealed that the phyllosilicates on asteroid (162173) Ryugu are dehydrated/dehydroxylated due to space weathering. Reactive molecular dynamics simulations were performed to evaluate the magnitude of the dehydroxylation of Mg-rich serpentine by micrometeoroid impacts. When micrometeoroids were not coupled with interplanetary magnetic fields, serpentine could be dehydroxylated by micrometeoroids as small as 2 nm in size. In particular, ~200 O-H bonds dissociated when the meteoroids were derived from cometary activity (the impact velocity was ~20 km s$^{-1}$). When nano-sized dust particles were accelerated to ~300 km s$^{-1}$ by the magnetic fields of solar wind plasma, the number of dissociated O-H bonds increased by one order of magnitude. Consequently even 1 nm-sized dust particles can contribute to the space weathering of Ryugu. In all cases, Si-OH, H2O, and free OH were generated from the hydroxyls initially connected to Mg, which could partially offset dehydration. Despite the limitations of our computational resources, which restricted the simulation time scale to 1 ps, reactive molecular dynamic simulations demonstrated that micrometeoroid bombardment could influence the space weathering of asteroids.
隼鸟2号的遥感观测和实验室测量结果表明，小行星（162173）龙宫上的植硅体由于空间风化而脱水/脱羟基。为了评估微流星体撞击造成富镁蛇纹石脱羟基的程度，进行了反应分子动力学模拟。当微流星体未与行星际磁场耦合时，蛇纹石可被尺寸小至 2 纳米的微流星体脱羟基。特别是，当流星体来自彗星活动（撞击速度约为 20 km s$^{-1}$）时，约有 200 个 O-H 键断裂。当纳米级尘埃粒子被太阳风等离子体的磁场加速到 ~300 km s$^{-1}$ 时，分离的 O-H 键数量增加了一个数量级。因此，即使是1纳米大小的尘埃粒子也会对龙宫的空间风化产生影响。在所有情况下，最初与镁相连的羟基都会产生Si-OH、H2O和游离OH，这可以部分抵消脱水作用。尽管我们的计算资源有限，将模拟时间尺度限制在 1 ps，但反应分子动力学模拟证明流星体轰击可以影响小行星的空间风化。
{"title":"Reactive molecular dynamics simulations of micrometeoroid bombardment for space weathering of asteroid (162173) Ryugu","authors":"Daigo Shoji","doi":"arxiv-2408.10959","DOIUrl":"https://doi.org/arxiv-2408.10959","url":null,"abstract":"Remote sensing observations by Hayabusa2 and laboratory measurements have\u0000revealed that the phyllosilicates on asteroid (162173) Ryugu are\u0000dehydrated/dehydroxylated due to space weathering. Reactive molecular dynamics\u0000simulations were performed to evaluate the magnitude of the dehydroxylation of\u0000Mg-rich serpentine by micrometeoroid impacts. When micrometeoroids were not\u0000coupled with interplanetary magnetic fields, serpentine could be dehydroxylated\u0000by micrometeoroids as small as 2 nm in size. In particular, ~200 O-H bonds\u0000dissociated when the meteoroids were derived from cometary activity (the impact\u0000velocity was ~20 km s$^{-1}$). When nano-sized dust particles were accelerated\u0000to ~300 km s$^{-1}$ by the magnetic fields of solar wind plasma, the number of\u0000dissociated O-H bonds increased by one order of magnitude. Consequently even 1\u0000nm-sized dust particles can contribute to the space weathering of Ryugu. In all\u0000cases, Si-OH, H2O, and free OH were generated from the hydroxyls initially\u0000connected to Mg, which could partially offset dehydration. Despite the\u0000limitations of our computational resources, which restricted the simulation\u0000time scale to 1 ps, reactive molecular dynamic simulations demonstrated that\u0000micrometeoroid bombardment could influence the space weathering of asteroids.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142221976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Biswajit Jana, EunKang Kim, Aayush Arya, Elisa Romero Romero, Elisabeth Rickert, Harry Ramanantoanina, Sebastian Raeder, Michael Block, Mustapha Laatiaoui
Relativistic effects strongly influence the electronic structures of the heaviest elements, thereby shaping their chemical and physical properties. Studying ion mobility within a noble gas environment reveals how the ion-neutral interactions depend on the ion's electronic configurations, thus providing an avenue for exploring these effects. An ion mobility spectrometer with a cryogenic drift tube was developed to precisely measure the low-field reduced mobility of heavy lanthanide and actinide cations. The apparatus was characterized by optimizing the bunching operation of ions with a miniature RF coulomb buncher and evaluating the chromatography performance of the drift tube operated with helium buffer gas at a temperature of 298K. Systematic ion mobility measurements of lutetium cations (Lu$^{+}$) drifting in helium gas were carried out as a case study. The electronic state chromatography of Lu$^{+}$ has been demonstrated. The low-field reduced ion mobility for the ground and lowest meta-stable state of Lu$^{+}$ have been examined. In addition, the variation of both states' reduced mobility and the quenching of meta-stable population has been investigated under different reduced electric fields ($E/n_0$), the ratio of an electric field to neutral gas number density.
{"title":"Electronic State Chromatography of Lutetium Cations","authors":"Biswajit Jana, EunKang Kim, Aayush Arya, Elisa Romero Romero, Elisabeth Rickert, Harry Ramanantoanina, Sebastian Raeder, Michael Block, Mustapha Laatiaoui","doi":"arxiv-2407.10851","DOIUrl":"https://doi.org/arxiv-2407.10851","url":null,"abstract":"Relativistic effects strongly influence the electronic structures of the\u0000heaviest elements, thereby shaping their chemical and physical properties.\u0000Studying ion mobility within a noble gas environment reveals how the\u0000ion-neutral interactions depend on the ion's electronic configurations, thus\u0000providing an avenue for exploring these effects. An ion mobility spectrometer\u0000with a cryogenic drift tube was developed to precisely measure the low-field\u0000reduced mobility of heavy lanthanide and actinide cations. The apparatus was\u0000characterized by optimizing the bunching operation of ions with a miniature RF\u0000coulomb buncher and evaluating the chromatography performance of the drift tube\u0000operated with helium buffer gas at a temperature of 298K. Systematic ion\u0000mobility measurements of lutetium cations (Lu$^{+}$) drifting in helium gas\u0000were carried out as a case study. The electronic state chromatography of\u0000Lu$^{+}$ has been demonstrated. The low-field reduced ion mobility for the\u0000ground and lowest meta-stable state of Lu$^{+}$ have been examined. In\u0000addition, the variation of both states' reduced mobility and the quenching of\u0000meta-stable population has been investigated under different reduced electric\u0000fields ($E/n_0$), the ratio of an electric field to neutral gas number density.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141718809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sascha Schaller, Johannes Seifert, Giacomo Valtolina, André Fielicke, Boris G. Sartakov, Gerard Meijer
Several diatomic transition metal oxides, rare-earth metal oxides and fluorides have the unusual property that their bond dissociation energy is larger than their ionization energy. In these molecules, bound levels above the ionization energy can be populated via strong, resonant transitions from the ground state. The only relevant decay channel of these levels is autoionization; predissociation is energetically not possible and radiative decay is many orders of magnitude slower. Starting from translationally cold neutral molecules, translationally cold molecular ions can thus be produced with very high efficiency. By populating bound levels just above the ionization energy, internally cold molecular ions, exclusively occupying the lowest rotational level, are produced. This is experimentally shown here for the dysprosium monoxide molecule, DyO, for which the lowest bond dissociation energy is determined to be 0.0831(6) eV above the ionization energy.
{"title":"Cold molecular ions via autoionization below the dissociation limit","authors":"Sascha Schaller, Johannes Seifert, Giacomo Valtolina, André Fielicke, Boris G. Sartakov, Gerard Meijer","doi":"arxiv-2406.03160","DOIUrl":"https://doi.org/arxiv-2406.03160","url":null,"abstract":"Several diatomic transition metal oxides, rare-earth metal oxides and\u0000fluorides have the unusual property that their bond dissociation energy is\u0000larger than their ionization energy. In these molecules, bound levels above the\u0000ionization energy can be populated via strong, resonant transitions from the\u0000ground state. The only relevant decay channel of these levels is\u0000autoionization; predissociation is energetically not possible and radiative\u0000decay is many orders of magnitude slower. Starting from translationally cold\u0000neutral molecules, translationally cold molecular ions can thus be produced\u0000with very high efficiency. By populating bound levels just above the ionization\u0000energy, internally cold molecular ions, exclusively occupying the lowest\u0000rotational level, are produced. This is experimentally shown here for the\u0000dysprosium monoxide molecule, DyO, for which the lowest bond dissociation\u0000energy is determined to be 0.0831(6) eV above the ionization energy.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141548786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Perfluorocubane ($C_8F_8$) was successfully synthesized and found to accept and store electrons in its internal cubic cavity to form magnetic moments. However their inter-molecule spin-exchange coupling mechanism is yet to be revealed. In this study, we found the inter-molecule magnetic groundstates of $C_8F_8$ dimer and one-dimensional (1D) chain are tunable from antiferromagnetic (AFM) to ferromagnetic (FM) by stacking orders and alkaline earth metals intercalation using first-principle calculations. The inter-molecule couplings are dominated by noncovalent halogen $C-F...C_4$ interactions. Stacking orders of dimers can regulate the relative position of the lone pairs and $sigma-holes$ at the molecular interface and thus the magnetic groundstates. Alkaline earth metals M (M = Na, Mg) intercalations could form $C_4-M-C_4$ bonds and lead to FM direct exchange at the inter-molecule region. An unpaired electron donated by the intercalated atoms or electron doping can result in a local magnetic moment in dimers, exhibiting an on-off switching by the odd-even number of electron filling. Novel electronic properties such as spin gapless semiconductor and charge density wave (CDW) states emerge when $C_8F_8$ molecules self-assemble with intercalated atoms to form 1D chains. These findings manifest the roles of stacking and intercalation in modifying intermolecular magnetism and the revealed halogen bond-dominated exchange mechanisms are paramount additions to those previously established non-covalent couplings.
{"title":"Alkaline earth metal mediated inter-molecular magnetism in perfluorocubane dimers and chains","authors":"Zhuohang Li, Cong Wang, Linwei Zhou, Yurou Guan, Linlu Wu, Jiaqi Dai, Wei Ji","doi":"arxiv-2405.12060","DOIUrl":"https://doi.org/arxiv-2405.12060","url":null,"abstract":"Perfluorocubane ($C_8F_8$) was successfully synthesized and found to accept\u0000and store electrons in its internal cubic cavity to form magnetic moments.\u0000However their inter-molecule spin-exchange coupling mechanism is yet to be\u0000revealed. In this study, we found the inter-molecule magnetic groundstates of\u0000$C_8F_8$ dimer and one-dimensional (1D) chain are tunable from\u0000antiferromagnetic (AFM) to ferromagnetic (FM) by stacking orders and alkaline\u0000earth metals intercalation using first-principle calculations. The\u0000inter-molecule couplings are dominated by noncovalent halogen $C-F...C_4$\u0000interactions. Stacking orders of dimers can regulate the relative position of\u0000the lone pairs and $sigma-holes$ at the molecular interface and thus the\u0000magnetic groundstates. Alkaline earth metals M (M = Na, Mg) intercalations\u0000could form $C_4-M-C_4$ bonds and lead to FM direct exchange at the\u0000inter-molecule region. An unpaired electron donated by the intercalated atoms\u0000or electron doping can result in a local magnetic moment in dimers, exhibiting\u0000an on-off switching by the odd-even number of electron filling. Novel\u0000electronic properties such as spin gapless semiconductor and charge density\u0000wave (CDW) states emerge when $C_8F_8$ molecules self-assemble with\u0000intercalated atoms to form 1D chains. These findings manifest the roles of\u0000stacking and intercalation in modifying intermolecular magnetism and the\u0000revealed halogen bond-dominated exchange mechanisms are paramount additions to\u0000those previously established non-covalent couplings.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"2014 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141148382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The optical absorption spectra of cyclo[n]carbons (n=10, 14, 18) are investigated in the framework of time-dependent density functional theory. The collective plasmon excitations well develop as the increases of the ring size and the symmetry group of cyclo[n]carbons. An increase in intensity for the main peaks with the growing number of atoms in cyclo[n]carbons is observed. With the increase of the radius of the monocyclic ring, as more electrons participate in the dipole oscillation the main excitation peaks are red-shifted to the lower energy. The highly symmetrical structures of cyclo[n]carbons (D_{nh}) possess degenerate levels, leading to simpler spectra with fewer peaks. The Fourier transform of the induced electron density of the cyclo[n]carbons (n=10, 14, 18) is investigated at the excitation frequencies.
{"title":"Theoretical investigation on the optical absorption spectra in cyclo[n]carbons (n=10, 14, 18)","authors":"Xuhai Hong, Lang Su, Jie Li","doi":"arxiv-2403.19952","DOIUrl":"https://doi.org/arxiv-2403.19952","url":null,"abstract":"The optical absorption spectra of cyclo[n]carbons (n=10, 14, 18) are\u0000investigated in the framework of time-dependent density functional theory. The\u0000collective plasmon excitations well develop as the increases of the ring size\u0000and the symmetry group of cyclo[n]carbons. An increase in intensity for the\u0000main peaks with the growing number of atoms in cyclo[n]carbons is observed.\u0000With the increase of the radius of the monocyclic ring, as more electrons\u0000participate in the dipole oscillation the main excitation peaks are red-shifted\u0000to the lower energy. The highly symmetrical structures of cyclo[n]carbons\u0000(D_{nh}) possess degenerate levels, leading to simpler spectra with fewer\u0000peaks. The Fourier transform of the induced electron density of the\u0000cyclo[n]carbons (n=10, 14, 18) is investigated at the excitation frequencies.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140595347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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